Jackknifing

In extreme circumstances, a driver may attempt to jackknife the vehicle deliberately to halt it following brake failure.

This is not the same as jackknifing and is not as serious, as the trailer will move back into line as the vehicle continues forwards.

This situation can occur especially when the trailer is empty or lightly loaded, and weather conditions cause violent gusts of crosswind.

Fitted originally to airplanes in the 1950s, anti-lock brakes have significantly reduced the number of heavy-vehicle accidents.

Trolley brakes largely disappeared from tractor units in North America in the 1980s and 1990s.